The purpose of this study is to determine whether LJP 394 is more effective than placebo in preventing renal flare in patients with a prior history of lupus renal disease. This multicenter, double-blind, randomized, placebo- controlled study will enrol approximately 400 patients and is composed of three periods: a screening/qualifying period, a double-blind, placebo- controlled treatment period, and a follow-up assessment period. This is an 18 month trial, with patients completing 61 visits.